On Mon, Oct 23, 2017 at 6:40 AM, Антонио Антуан <a.ch....@gmail.com> wrote:
> Hello guys.
>
> I try to make my own GenericFunction with default compiler and custom
> compiler for particular dialect. As you see below, always used custom
> compiler:
>
> from sqlalchemy import func, create_engine, Integer
> from sqlalchemy.ext.compiler import compiles
> from sqlalchemy.orm import sessionmaker
> from sqlalchemy.sql.functions import GenericFunction
>
> engine_ch = create_engine('clickhouse+native://log:pas@127.0.0.1:9000/db')
> engine_pg = create_engine('postgresql://log:pas@127.0.0.1:9000/db')
>
> ses_pg = sessionmaker(bind=engine_pg)()
> ses_ch = sessionmaker(bind=engine_ch)()
>
>
> class IntDiv(GenericFunction):
> type = Integer
> package = 'custom'
> name = 'div'
> identifier = 'div'
>
>
> @compiles(IntDiv)
> def visit_div_default(element, compiler, **kwargs):
> return 'div(%s)' % compiler.process(element.clause_expr.element)
>
>
> @compiles(IntDiv, 'clickhouse')
> def visit_div_ch(element, compiler, **kwargs):
> return 'intDiv(%s)' % compiler.process(element.clause_expr.element)
>
>
> print(ses_ch.bind.dialect.name)
> print(ses_ch.query(func.custom.div(1, 2)))
>
> print(ses_pg.bind.dialect.name)
> print(ses_pg.query(func.custom.div(1, 2)))
>
>
> If I not make "@compiles(IntDiv)" (for default dialct), make only
> @compiles(IntDiv, 'clickhouse) I got this error:
>
> Traceback (most recent call last):
> File "/home/anton/Projects/proj/core/run/stuff.py", line 31, in <module>
> print(ses_ch.query(func.custom.div(1, 2)))
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/orm/query.py",
> line 3457, in __str__
> return str(self._compile_context().statement)
Based on that line number, I can see you are on a 1.0.x version of
SQLAlchemy. Query.__str__() takes into account the bound dialect
automatically as of 1.1:
http://docs.sqlalchemy.org/en/latest/changelog/migration_11.html#stringify-of-query-will-consult-the-session-for-the-correct-dialect
if you are on 1.0.x or earlier you need to compile from the statement:
query.statement.compile(my_engine)
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/elements.py",
> line 506, in __str__
> return unicode(self.compile()).encode('ascii', 'backslashreplace')
> File "<string>", line 1, in <lambda>
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/elements.py",
> line 494, in compile
> return self._compiler(dialect, bind=bind, **kw)
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/elements.py",
> line 500, in _compiler
> return dialect.statement_compiler(dialect, self, **kw)
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py",
> line 395, in __init__
> Compiled.__init__(self, dialect, statement, **kwargs)
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py",
> line 190, in __init__
> self.string = self.process(self.statement, **compile_kwargs)
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py",
> line 213, in process
> return obj._compiler_dispatch(self, **kwargs)
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/visitors.py",
> line 81, in _compiler_dispatch
> return meth(self, **kw)
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py",
> line 1584, in visit_select
> for name, column in select._columns_plus_names
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py",
> line 1357, in _label_select_column
> **column_clause_args
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/visitors.py",
> line 93, in _compiler_dispatch
> return meth(self, **kw)
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py",
> line 615, in visit_label
> OPERATORS[operators.as_] + \
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/ext/compiler.py",
> line 423, in <lambda>
> lambda *arg, **kw: existing(*arg, **kw))
> File
> "/home/anton/Projects/proj/.venv/lib/python2.7/site-packages/sqlalchemy/ext/compiler.py",
> line 460, in __call__
> "compilation handler." % type(element))
> sqlalchemy.exc.CompileError: <class '__main__.IntDiv'> construct has no
> default compilation handler.
>
>
> Is it possible to override default GenericFunction compiler?
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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